Method and apparatus of continuous steam-atomizing fuel combustion for boiler furnace

ABSTRACT

A METHOD AND APPARATUS FOR INITIATING COMBUSTION IN A STEAM-ATOMIZING FURNACE USING A PRESSURIZED SOURCE OF COMBUSTION AIR TO ATOMIZE THE FUEL DURING STARTUP WHEN THE STEAM PRESSURE IS INSUFFICIENT TO DO SO. A DAMPER IS PROVIDED IN THE AIR INLET TO BUILD UP THE AIR PRESSURE UPSTREAM OF THE DAMPER SO THAT THE LATTER AIR PRESSURE MAY BE DIRECTED THROUGH THE ATOMIZING NOZZLE. WHEN THE   FURNACE IS UP TO TEMPERATURE AND STEAM IS GENERATED BY THE FURNACE, THE DAMPER IS OPENED TO OBTAIN EFFICIENT COMBUSTION OF THE FUEL WHICH IS THEN ATOMIZED BY THE STEAM. A SUPPLEMENTAL AIR HEATER IS PROVIDED TO ELEVATE THE TEMPERATURE OF THE PRESSURIZED AIR DURING THE STARTUP.

June 27, 1972 SHUZO MIYAZAKI 3,672,808

METHOD AND APPARATUS OF CONTINUOUS STEAM-ATOMIZING FUEL COMBUSTION FORBOILER FURNACE Filed Oct. 15. 1970 2 sheets sheec l f lf June 27, 1972SHUZO MIYAZAKI 3,672,303

METHOD AND APPARATUS 0F CONTINUOUS STEAM-ATOMIZING FUEL COMBUSTION FORBOILER FURNACE zsheets sheet 2 Filed Oct. 15, 1970 United States PatentMETHOD AND APPARATUS 0F CONTINUOUS STEAM-ATOMIZING FUEL COMBUSTION FORBOILER FURNACE Shuzo Miyazaki, Tokyo, Japan, assignor to Japan FurnaceIndustry Co. Ltd., Tokyo, Japan Filed Oct. 15, 1970, Ser. No. 80,906Int. Cl. F23n 1/04 U.S. Cl. 431-2 Claims ABSTRACT OF THE DISCLOSURE Amethod and apparatus for initiating combustion in a steam-atomizingfurnace using the pressurized source of combustion air to atomize thefuel during startup when the steam pressure is insuificient to do so. Adamper is provided in the air inlet to build up the air pressureupstream of the damper so that the latter air pressure may be directedthrough the atomizing nozzle. When the furnace is up to temperature andsteam is generated by the furnace, the damper is opened to obtaineflicient combustion of the fuel which is then atomized by the steam.

.A supplemental air heater is provided to elevate the temperature of thepressurized air during the startup.

This invention relates to method and apparatus of continuoussteam-atomizing fuel combustion for boiler furnace of forced draftcombustion system.

Generally there are various types of oil burners for steam boiler usesuch as oil pressure type, rotary type, low pressure or high pressureair-atomized oil burner, steam-atomizing oil burner. Among theseconventional burners, the steam-atomizing oil burner has been preferablyavailable because of its merits that (1) steam generated in the boilermay be directly used as an atomizing medium, and that (2) the very highturn-down ratio of combustion amount permits the burner to easily followthe load variation in the steam boiler. Especially the recent trend ofreducing the size of combustion chamber of steam boiler itself, andusing a high pressure in furnace requires a high-pressure, high-loadedcombustion oil burner. This rapidly increases the demand for asteamatomizing burner. For example, the turn-down ratio of burner ischanging from the conventional ratio 10:4 to 10:1 or 12:1. The furnacepressure is also changing from the conventional -50 mm., column ofWater, to 150- 300 mm., column of water. The combustion chamber load isalso changing from 200,000 Kcal./m. hr. to l,500,0002,500,000 Kcal./m.hr. Such technical requirements have developed an increasing applicationfor a steam atomizing burner because of its high-loaded combustion andwide range controllability. On the other hand, operation of the steamboiler is rapidly being automated. Almost all small-sized steam boilersof evaporation amount of less than 30 t./h. have adopted semiautomaticor full automatic operation system. Since a steam atomizing burner maynot be operated under the steamless condition in automatic operation,(1) the operation should be started by the aid of a starter oil pressureburner until steam generates and then the burner is changed to a steamatomizing burner for continuing operation, or (2) an air compressorshould be separately provided for making an atomized air flow at thetime of starting. If there is a steam source, the steam from this sourcemay be used for starting, but such a steam source is rarely available inthe site where a relatively small sized boiler is installed. Moreoveralmost all of small-sized boilers which are, as a general rule,controlled in an unattended manner, rely upon starter button system forautomatic operation, so that it should essentially be operatedcontinuously from starting.

An object of the newly developed apparatus of the present invention isto fulfill these requirements, that is, to utilize the excellenthigh-loaded combustion caused by steam injection and to maintaincontinuous operation from starting to normal operation. In view of thefact that almost all of smallor medium-sized boilers of the day use aforced draft combustion system provided with a blower for supplyingcombustion air, the present invention has for its feature to utilize thehigh pressure air of the blower as atomizing air, thereby establishingeasy starting and automatic change for continuous operation veryeconomically without any separate source of air flow for atomizations.

The structure and operation of the present invention will be nowexplained in detail with reference to the accompanying drawings, inwhich:

FIG. 1 is a vertical sectional view of a fuel burner of the presentinvention;

FIG. 2 is an enlarged sectional view of FIG. 1, illustrating operationof the steam-atomizing burner under steamless starting condition;

FIG. 3 is a front view taken from the right end face of FIG. 2; and

FIG. 4 is a flow sheet showing the connection between the feed of fueland steam in the burner of the present invention and the blast from ablower.

Referring to FIG. 1, there is shown a vertical sectional view of anembodiment of the oil burner according to the present invention. The oilburner illustrated is fixed to a front wall b of a boiler furnace. Awind box 7 of cylindrical configuration is fluid-connected to asecondary combustion air inlet duct 8 which is integrally provided witha combustion air adjusting dumper 6. The wind box 7 is fixed to a frontpanel 'F of a boiler furnace wall b by a front plate-mounting flange f.The furnace wall b for the front panel F is provided with afunnel-shaped burner tile hole 15 for stabilizing combustion. On insideof the front surface of the wind box 7 is concentrically provided an airrectifying cylinder 9 with suitable openings, said cylinder is connectedto a burner throat 14 reduced radially at its middle portion. The airfed through air rectifying cylinder 9 is portionally throttled at theburner throat 14 and then fed into the furnace along inside surface ofthe burner tile hole 15 while expanding toward the interior of thefurnace. Air deflectors 5 are provided all over the inside wall ofburner throat 14. The air deflectors 5 are each arranged with a fixedangle relative to the axis line of the throat so as to cause the airintroduced along inside wall of the throat to swirl. A steam atomizer 12is built in the'central portion of an atomizing cylinder 4 which isprovided through the central portion of the air cylinder 9 and throat14. As shown in detail in FIG. 2, an air inlet passage 3 provided in thebase portion of the atomizing cylinder 4 receives atomizing air from anintermediate passage between the air flow adjusting dumper 6 in the airinlet duct 8 of the blower S and an outlet of the same blower so as tointroduce the primary air directly into the atomizing cylinder 4. In thebase portion of atomizer 12 passing through the center of the atomizingcylinder 4 is provided an atomizing steam inlet 2 and a fuel inlet pipe1 as explained in detail hereinafter. A swirler 11 provided on the outerperiphery of the end portion of the atomizing cylinder 4 causes the airintroduced in the proximity of the atomizing cylinder 4 to stabilize thefiring. Reference numeral 10 denotesan air inlet cylinder attached tothe swirler 11. An atomizer holder 20 is provided in the middle portionof the atomizing cylinder 4. An atomizer body 21 is provided at the endof the holder 20 and a flange 27 provided in the middle portion of theatomizer body 21 is fixed to outer cylinder 4 by screws 22. The innersurface of the atomizer body 21 is cylindrical at its basic portion andtapered outwardly toward the end into a cup-like shape 23. Thecylindrical base portion of the atomizer body 21 is tangentiallyprovided at'three locations therein with air inlet slits 25. The flange27 in the middle of the atomizer body 21 is provided with a number ofair ducts 28. The foremost end of the cup 23 makes an annular airpassage 29 at a clearance between the atomizing cylinder 4 and thecup-shaped portion 23. Accordingly, the air introduced from the airinlet passage 3 into the atomizing cylinder 4 is partially guided in thechamber 16 of said atomizer body 21 through the tangential slits 25 andproceeds along the inner surface of said atomizer body 21, together withmaking swirling movements. The rest of the air outside the atomizer body21 passes through the air duct 28 of the atomizer flange 27 and thenruns through the annular slit 29 and is released into the furnace. Thesteam atomizer 30 provided at the center of the atomizer holder 20 andatomizer body 21 may be of any one of external mixing types. Inaccordance with the present invention, the steam atomizer is arrangedsuch that the fuel oil is jetted out from a plurality of nozzle orificeswhich are substantially perpendicular to the axis of the atomizer.

In the ambodiment shown in FIG. 2, atomizing steam introduced from thesteam inlet 2 through the clearance between the outer cylinder 30 of theatomizer and the oil pipe 31 provided at the center of said holder andcylinder proceeds through the steam passage of a sprayer body 32 andleaves the clearance between the sprayer body and the tip of a cap nut33. The oil proceeds through the oil pipe 1 and the oil passage 35 atthe center of the spray body 32 and leaves oil outlet port 36 along thenormal direction. A substantially semi-spherical impact head 37 isprovided at the tip end of the oil pipe 31, so that the oil injected inthe normal direction encounters with steam injected and impinges on theimpact head 37. Thus, the oil spreads in the form of fine mistyparticles and is completely mixed with the air. The mixture is thenforced into the furnace and gasified by heat so as to burnsatisfactorily. When there is no steam at the time of starting, only oilis injected from the port 36. Now assuming the. nozzle is placed at anappropriate position of the opening of atomizer body 21 (for example asshown in FIG. 2), the oil injected first impinges upon the inner wall ofthe cup of said atomizer body 21 and then is introduced throughtangential air from said air ports 15 of the atomizer body, and thenspread divergently with the swirling air. The atomized oil is thuscarried by the air flow along the cup edge 23 of the atomizer body andinjected in the form of thin film or vapor in the same manner as in therotary-cup atomizer. This oil film is finely atomized by high speedy airjet from the circumferentially-spaced passage of the atomizer. Forobtaining high atomizing effect, it is, of course necessary to keep alarger momentum of the air, more especially. It is important to maintaina certain pressure head. For instance, in case of a small-sized boilerhaving the furnace static pressure of 300 mm. column of water at maximumload and the wind box static pressure of 500 mm. column of water i.e.the absolute differential pressure of 200 mm. column of water, theblower is generally designed to have the static pressure of 600-700 mm.column of water, with taking pressure loss in the piping intoconsideration. Now supposing that the combustion amount is M at burnerstarting, the furnace pressure should be i.e. about 3 mm. column ofwater. In this condition, further assuming that a blower having thestatic pressure of 600 mm. column of water is operated with air flow of,5 as throttling the dumper, the static pressure will be higher than 700mm. column of water, depending upon the characteristic of the blower.This static pressure of about 700 mm., used as the atomizing airpressure at the time of starting will be suflicient for atomization.With generation of steam after starting, the steam automatically flowsinto the atomizer whereby the steam-atomizing burner is automaticallyturned into-its operative condition. Although the difierential pressurebetween the discharge pressure of the blower and the furnace pressuregradually decreases with increase' of the boiler load, no problem foratomization occurs because the air discharged from the atomizer onlyacts for combustion, not for atomization, after generation of steam.

FIG. 4 shows a flow sheet when the present device is installed to theboiler. The main combustion air inlet passage 8 starting from the blowerS is connected to the wind box 7 through the dumper 6 and then branchesair passage 3 to feed air directly to the atomizing cylinder 4. Theatomizing steam is led directly from a boiler header 40 or a steamreservoir to the steam inlet 2 of the atomizer through a piping 41having therein a solenoid-operated valve 42. A drain trap 38 provided atthe steam inlet 2 of the atomizer serves to feed dry steam to theatomizer 30 as soon as steam generates in the boiler. It will be thusunderstood that the fuel atomization is automatically turned into thesteam atomizing manner. The amounts of combustion air flow and fuel aresimultaneously controlled by a dumper 6 and an oil regulating valve 43.must be preferably given to the air. For such purpose in the presentinvention, small amount of suitable gas, such as liquid pressure gas, isburnt in the air inlet duct 3 and the burnt gas is to be mixed to theprimary air to prepare heated air of 200-400 C. to atomize the oil. I

As shown in FIG. 2, a cylindrical ceramic pipe having a combustionchamber 144 therein is supported on the stays 146 in the air inlet pipe3 leaving a space between the air inlet pipe 3 and ceramic pipe 145. Tosaid chamber 144 of said ceramic pipe, a gas burner pipe 147 is insertedfrom under side and a gas igniting electric terminal 148 is insertedfrom upper side near the burner I running may be improved. As stated, asmall amount of' gas, such as liquid pressure gas, is burned in the gasburner 147 the primary air is heated about 300 C. The gasification ofthe atomized oil becomes easy by the heated primary air and burningspeed may be improved and continuous steady burning is obtained.Moreover, as theburnt gas in the gas burner is mixed to the primary air,

nitrogen compound in the exhaust gas from the furnace is remarkablyreduced.

What I claim is:

1. A continuous steam-atomizing fuel combustion method in asteam-atmozing fuel combustion apparatus for boiler use of forced draftcombustion system, characterized by throttling a discharge opening of ablower of combustion air, thereby highly pressurizing the air in an airpipe when there is no steam in starting the boiler, and feeding the highpressure air into the atomizing burner thereby atomizing the fuel,firing the fuel for starting combustion, after that when steam generatesin said boiler, performing atomization by the pressure of the steam andat the same time releasing said throttled condition of the blowerthereby lowering the air pressure, and simultaneously increasing theblast into the wind box, thus automatically the atomization under thesteamless condition is switched over to the steam atomization.

2. An apparatus for continuous steam-atomizing fuel combustion,characterized by a wind box fixed to a boiler furnace, pressure means tosupply combustion air including an air inlet duct, said wind box beingconnected to said combustion air inlet duct, an air flow control damperin said duct, an air atomizing cylinder provided at the center of saidwind box, an air duct pipe branching from said duct between saidpressure air supply and said damper, said branch pipe connected as anair inlet to said atomizing cylinder, a steam atomizer 30 provided inthe atomizing cylinder, means to connect said steam atomizer to steampipes of the boiler; and a controller responsive to the steam pressurecreated in the boiler to open said damper whereby fuel atomization maybe automatically changed to the steam-atomization by the action of thesaid steam pressure.

3. Apparatus acocrding to claim 2 including a gas burner in said branchpipe to raise the temperature of the air forced through said pipe byclosure of said damper.

4. Apparatus according to claim 3 wherein said gas burner comprises aceramic annular element disposed substantially coaxially within saidpipe and a gas supply pipe projecting axially into said annular elementand terminating therein to constitute said burner.

5. Apparatus according to claim 4 including a gasigniting electricterminal mounted in said annular member adjacent said burner pipe togenerate electric sparks for igniting the gas.

6. Apparatus according to claim 2 including means to regulate the supplyof fuel to said cylinder, and connections from said controller to saidsupply-regulating means to adjust said supply concurrently withadjustment of said damper.

7. Apparatus according to claim 6 including a heater to heat the fuelsupplied to said atomizing cylinder, and connections from saidcontroller to said heater.

8. Apparatus according to claim 2 including means to sense the steampressure in the connection between said steam atomizer and the steampipes, said sensing means being connected to said controller to effectsaid response to the steam pressure in the boiler.

9. Apparatus according to claim 2 wherein said pressure means to supplycombustion air comprises a blower having its exhaust coupled to said airinlet duct.

10. Apparatus according to claim 2 wherein said damper comprises a platemounted for pivotal movement in said air inlet duct.

References Cited UNITED STATES PATENTS 1,598,866 9/1926 Lovell 431-191,599,137 9/1926 McLean 431-19 1,681,663 8/1928 Faickney 431216 EDWARDG. FAVORS, Primary Examiner US. Cl. X.R. 43189, i

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,672,808 Dated June 27, 1972 Inventor s) Shuzo Miyazaki It is certifiedthat error appears in the above-identified patent and that said Letters.Patent are hereby corrected as shown below:

In the heading change the Applicant to --Shuzo Miyazaki,

Tokyo, Japan-- Signed and sealed this 11h; day r ma "1971+,

(SEAL) Attest:

EDIARD H.FLE'1'CEER,JR. Attesting Officer C. MARSHALL DANN Commissionerof Patents USCOMM'DC 6376'PU9 i U.S GOVERNMENT PRINTING OFFICQ Ill0-80-834.

FORM PO-105D (10-69)

